Continuation of support is requested for a multidisciplinary center to study the basic pathologic mechanisms of certain skin diseases which appear to have the participation of humoral or cellular immunologic events, either as a primary or secondary manifestation. The center will concentrate in studies of: 1. Diseases within the spectrum of cutaneous vasculitis-angioedema-urticaria. In these studies we will attempt to identify the biochemical mediators and cellular interactions that may be responsible for the clinical manifestations in this group of diseases. 2. Receptors in patients presenting with clinical manifestations within the spectrum of altered immunologic reactivity. These studies will involve patients with: acquired deficiency syndrome, lupus erythematosus and Hansen's disease. It is proposed that complement receptors may be predictive markers of disease activity. 3. Phototoxic reactions either due to genetic defects in phorphyrin metabolism or intake of medications. These diseases offer an excellent model for studies of non-immunologic activation of the complement system and mast cell derived mediators.